This study is to determine the ultrastructural pathogenesis of the myelopathy associated with C-type virus in the spontaneous and induced murine paralysis discovered by Gardner and co-workers. Spontaneously paralyzed mice will be studied after the onset of clinical paralysis while those with induced paralysis will be serially studied prior to clinical disease. All animals, after being anesthetized, will be perfused via the heart; the spinal cord and other tissue will then be removed for further gross sectioning for appropriate EM samples, preparation, and EM study. These studies should demonstrate the sequence of spinal cord tissue involvement, the effects of viral infection on the various cellular elements, and whether changes not associated with cellular viral infection occur. These findings, together with a survey of other nervous tissue for changes associated with viral infection, may increase our understanding of the pathogenesis of slow or latent viral infections in the nervous system.